The invention relates generally to a local wireless communication system and, more particularly, to a wireless communication system using radio frequencies for transmitting and receiving voice and data signal with an internal network with multiple internal communication paths, and an external communication path for linking the internal network to an external communications network.
Wireless communication systems continue to grow, particularly in the areas of cellular and digital telephony and in paging systems. Wireless systems are especially popular in remote areas of the world that have limited wired service because of the cost and difficulty of building a wired infrastructure.
Current traditional wireless communication systems such as cellular telephones, use radio communications between a plurality of subscriber units within the wireless system and between subscriber units and the Public Switch Telephone Network (PSTN) for calls that are outside of the wireless system. Most of these systems are characterized by wireless mobile telephone units communicating with base stations that are connected to centralized mobile switching centers (MSC), that are in turn connected to the PSTN. The centralized MSC performs a number of functions, including routing wireless mobile units calls to other mobile units and wired (land-line) users and routing land-line calls to mobile units. The MSC accomplishes this by being connected to base stations for accessing mobile users and by being connected to the PSTN for accessing users outside the wireless system, be they other wireless users in other wireless systems or land-line users. Therefore the MSC functions, as its name implies, as a switching and routing center that controls the overall operation of the systems. This results in a centralized calling system with the MSC being involved in routing all the calls to and from the wireless system. This centralization allows the MSC to be the primary collection point for compiling billing information for its wireless mobile units. The centralized MSC also creates a need for expensive infrastructure equipment. As more mobile telephone units are added to the system, the MSC must in turn expand to be able to handle the additional volumes of phone calls, connections and the associated billing services. In addition, since the base stations provide the connection to the mobile units, a large increase in the number of mobile units within an area covered by the base station can overload the base station, thus requiring more base stations and/or enhancing the capabilities of the base stations.
Others systems use point-to-point radio communications where mobile units may communicate with other mobile units in the local area. They send origin and destination address information and make use of squelching circuits to direct the wireless transmission to the correct destination address. Most of these systems do not appear to provide a connection to a PSTN to send and receive calls outside the wireless network. This type of system is decentralized, but because of the decentralization, collecting accurate billing information may be a problem.
However, most wireless systems still require a centralized system where a wireless base station (fixed or mobile) operates through a centralized switching center for communication within the wireless network and for communication outside the wireless network, for example to a PSTN. In many cellular and digital wireless systems, base station controllers cover a geographical area and are connected to a mobile services switching center. When a cellular or digital mobile unit places a call, the call is routed to the base station controller serving the mobile unit's geographical area and the base station controller connects the unit to the centralized switching center which in turn routes the call to its appropriate destination. As more wireless units come online in a geographical area, base station controllers and switching centers must be added or upgraded.
Another form of wireless system is called a local multipoint distribution service (LDMS). In an LMDS system, a local area or cell that is approximately 4 km in diameter contains fixed base stations, geographically distributed throughout the local area. One or more antennas within the local area receive calls from the fixed base stations and relay the calls to other fixed base stations. In order for the system to work, the fixed base stations must be within the line-of-sight path of at least one of the antenna units. The LDMS does not provide for mobile stations. Calls can only be routed within the local area and not to an external network. The system is essentially a centralized system within a local area. If one station is not within the line of sight of the antenna, it is effectively cut off from communication.
Therefore there is a need for decentralized wireless communications system for voice and data communication that allows for a flexibility of communication paths, provides local communication as well as optional links to external networks, such as public switch telephone networks, satellites and radio emergency networks, does not require a centralized switching center, provides for secure operation, allows for control the operational state of the internal network, provides for emergency notification and provides a way to collect revenue from the system.